1. Field of the Invention
The present invention relates generally to a system for rapidly detecting breakage of one or more of a plurality of strands of material that are being fed along an array of separate feed paths while the array of feed paths is being rotated about an imaginary axis that extends substantially centrally among the feed paths. More particularly, the present invention relates to the use of a plurality of strand breakage indicator assemblies that each are associated with a separate one of the feed paths for providing pivotally mounted flag-carrying indicator arms that are counterbalanced to render the arms substantially insensitive to centrifugal force and to changes in speed of rotation, with each of the arms being biased into engagement with a guided reach of an associated strand in a manner that will permit such tautness of the reach as is characteristic of normal feeding of the strand along its associated feed path to hold the associated flag-carrying arm in a "nested" position; however, if the associated strand should break, or if an undesired diminution in tautness of the guided reach of the associated strand is otherwise caused to take place, the associated flag-carrying indicator arm promptly will pivot to an "extended" position wherein it typically will be detected within less than one revolution of the array of feed paths by a stationary detector that monitors a circular path of travel that is followed by "extended" indicator flags.
2. Prior Art
While a variety of strand breakage detection systems have been proposed for use with apparatus that requires the concurrent feeding of a plurality of strands of material along separate feed paths to a workstation or the like, most of these prior proposals are not suited for use with apparatus that requires that a plurality of strands be fed in unison along an array of feed paths while the array is being rotated at relatively high speeds of rotation (e.g., within the range of about 600 to about 1400 revolutions per minute, and sometimes higher).
A significant problem that arises when structures that define arrays of feed paths are rotated at speeds as high as 1400 revolutions per minute is that the components of such structures must be capable not only of withstanding relatively high loadings of centrifugal force, but must also be capable of functioning properly in the presence of such loadings. At 1400 revolutions per minute, a component that is spaced only a few inches from the axis of rotation easily can be subjected to loadings of force that are hundreds of times the weight of the component. In such circumstances, electrical switch components easily can develop malfunctions and/or fail to perform as intended. Likewise, even simple mechanical devices that employ relatively movable parts and that have proven to be highly reliable when used in stationary environments often are found to malfunction and/or fail to perform as intended when subjected to an environment of high speed rotation.
While a number of proposals have been made that attempt to utilize electrical components and circuitry that is installed on rotating structures to provide for the sensing of breakage of one or more strands that are being fed in unison along arrays of feed paths that are defined by such structures, still another problem that typically renders such proposals unsuitable is that, of necessity, they employ some form of commutators to establish requisite electrical connections between the rotating structures and adjacent stationary structures. Such proposals not only characteristically suffer from the drawbacks and shortcomings described above, but also from the problems that typically are associated with the use of commutators. Commutators are subject to wear and often fail to supply with suitable stability the type of uninterrupted electrical contact that needs to be maintained between rotating and stationary structures. Thus, to the extent that the employment of commutators, electrical components and associated circuitry can be avoided on rotating structure that defines a plurality of strand feed paths, it has been deemed desirable to do so.
In commercially available knitting machinery of the type that typically is utilized in the formation of reinforced rubber hose to provide a knitted layer of reinforcing material that extends about an inner layer of the rubber hose, it often is desirable to rotate an assembly known as a "knitter" (i.e., a commercially available unit that employs knitting needles that are moved by a mechanical cam drive system and which needs to be supplied with a plurality of strands of material to be "knitted") at relatively high speeds of rotation together with such structure as defines an array of feed paths that are followed by strands of material that are fed in unison to the knitter. The faster that the knitter and the associated strand feed path defining structure can be rotated while suitably supplying an array of strands of material to the knitter, the greater the length of reinforced hose that can be produced during a given period of time. However, the faster that the strand-feeding structure is rotated, the greater are the centrifugal forces that are imposed on attendant strand breakage sensing components, and, if known types of strand breakage detector devices are employed, the greater is the likelihood that they will be deleteriously affected. A suitably simple, highly reliable strand breakage detection system that is capable of being used in such an environment long has eluded those who are skilled in the art.